Superconductivity and Magnetoresistance in NbSe2

Electron conduction in single crystals of Nb${\mathrm{Se}}_2$ has been measured at 4.2°K in magnetic fields up to 150 kOe. The upper critical field $H_{c2\mathrm{}}$ has been measured as a function of the angle between the applied field and the layers of the crystal for currents flowing both parallel and perpendicular to the layers. An effective-mass model based on simple considerations of the anisotropy of the crystal has been used to obtain a value for the ratio of effective masses for electron motion parallel and perpendicular to the layers, and the best value obtained is $\frac{m_{\parallel }}{m_{\perp }}=0.09\mathrm{}\pm 0.01$. Transverse-magnetoresistance rotation diagrams have been studied and structure due to flux flow and flux pinning has been observed.